1. Field of the Invention
The present invention relates to a plasma display panel(hereafter called as PDP), and more particularly, to a PDP with a varied thickness dielectric film.
2. Discussion of the Related Art
In general, the PDP is the most suitable for a flat display panel because the PDP has a fast data display rate and a large sized panel is available with easy. The PDP is suggested to be an AC type PDP or DC type PDP both with two electrodes, of which, it is known that a surface discharge type AC PDP is the most appropriate for a color display. The PDP is in general one of luminous device which uses gaseous discharge within each discharge cell for displaying an image. Because the PDP is simple to fabricate, easy to fabricate a large sized screen, and fast in response, it is spot lighted as a direct view image display with a large screen, particularly as a display directed to an age of HDTV.
FIG. 1 illustrates an overall perspective view of a related art surface discharge type AC PDP.
Referring to FIG. 1, the related art surface discharge type AC PDP is provided with, at large, a front substrate 1 for displaying an image, a rear substrate 2 disposed spaced from, and parallel to the front substrate 1, a plurality of barriers 3 arranged on the rear substrate 2 opposite to the front substrate 1 at fixed intervals, and a plurality of discharge spaces formed when the front substrate 1 and the rear substrate 2 are bonded. In detail, the PDP is provided with address electrodes 4 each provided between every adjacent barriers 3, a fluorescent film 5 formed on both walls of each barrier 3 in each of the discharge spaces and on the address electrode 4 on a bottom surface of each of the discharge spaces for emitting a visible light at discharge of the cell, and a display electrode 6 and a bus electrode 7 formed alternatively on the front substrate 1 opposite to the rear substrate 2. The display electrode 6 and a bus electrode 7 are formed in a direction perpendicular to a direction of the plurality of address electrodes 4, to have a plurality of cell discharge in an entire screen. There are a dielectric layer 8 formed on the display electrode 6 and a bus electrode 7 for restricting a discharge current, a protection layer 9 formed on the dielectric layer 8 for protecting the display electrode 6, the bus electrode 7, and the dielectric layer 8, and discharge gas in each discharge space for inducing the Penning effect.
FIG. 2 illustrates a cross section of a plurality of discharge cells in a related art surface discharge type AC PDP, wherein one pair of transparent electrodes 13 on a front substrate 11 are shown turned by 90xc2x0 for convenience of understanding. The display electrode 21 has a pair of a transparent electrode 13 and a metal electrode 22.
Referring to FIG. 2, the related art surface discharge type AC PDP is provided with a top panel having one pair of transparent electrodes 13 formed on a front panel 11, a first, and a second dielectric layers 14 and 15 on an entire surfaces of the pair the transparent electrodes 13 for restricting a discharge current, and a protection layer 16 formed on the second dielectric layer 15. And, there is a bottom panel having address electrode 17 formed on a region of a rear substrate 12 to cross the pair of transparent electrodes 13 in the top panel, barriers 19 for providing different colors between adjacent cells each with an address electrode 17, and a fluorescent material layer 18 formed on the barrier 19 and the address electrodes 17. There is Frit glass(not shown) bonding the front substrate 11 in the top panel and the rear substrate 12 in the bottom panel together and a mixture gas filled in discharge space 20 and sealed, completely.
In the aforementioned related art surface discharge type AC PDP, upon application of a discharge initiation voltage to one of the display electrodes 21 and an address signal to the address electrode 17 on the same time, a writing discharge is occurred in the discharge cell. That is, an electric field is established in the discharge cell, to accelerate a small amount of electrons present in the discharge gas to collide with neutral particles in the gas, causing ionization of the neutral particles into electrons and ions and another collisions of the ionized electrons with neutral particles, which again causes ionization of the neutral particles into electrons and ions at a faster rate, resulting to turn the discharge gas into a plasma state and cause a surface discharge 20a in the discharge space 20 from surfaces of the first, and second dielectric layers 14 and 15 and the protection layer 16, emitting a vacuum ultra-violet(uv) ray. This vacuum ray excites the fluorescent material layer 18, to cause the fluorescent material layer to emit a visible light, which is directed to outside of the panel through the front substrate 11, to display R, G, B color. That is, spatial charges present in the discharge space 20 are accelerated by a sustain voltage applied to each display electrode 21, and make collision with the inert gas filled in the discharge space 20 at 400xcx9c500 Torr, emitting the vacuum UV ray. The inert mixture gas has helium He as a major gas, and added with xenon Xe and neon Ne. The vacuum UV ray hits on the fluorescent material layer 18 on the address electrode 17 and the barrier 19, emitting a visible light. In other words, a color display is made by a combination of R, G, B, defined at least 3 luminescent regions.
It is required in the aforementioned PDP to reduce a discharge current for improving a luminous efficiency. This discharge current is substantially influenced by thicknesses of the first, and second dielectric layers 14 and 15 on the display electrode 21; if the first, and second dielectric layers 14 and 15 are thin, the discharge initiation voltage is in general low and the discharge current is increased, but if the first and second dielectric layers 14 and 15 are the more thicker, the discharge initiation voltage becomes the more lower and the discharge current becomes reduced the more. Therefore, if the dielectric layer is simply formed thicker, the discharge current may be reduced, but the discharge initiation voltage rises, making actual PDP driving difficult. Charges in the space after initiation of a discharge moves from {circle around (1)} to {circle around (2)} to cut off an external voltage and attached to surfaces of the first, and second dielectric layers 14 and 15 to drop a voltage in the discharge space. According to this, a waveform of the discharge current is formed in a form the discharge stops once the discharge is occurred. Since a tail portion of the discharge current serves nothing in the light emission but waste power, it is required to shorten the tail portion of the discharge current. The luminous efficiency can be defined by an equation (1), below.                               Luminous          ⁢                      xe2x80x83                    ⁢          Efficiency          ⁢                      xe2x80x83                    ⁢                      (                          lm              ⁢                              /                            ⁢              W                        )                          =                              luminance            ⁢                          xe2x80x83                        ⁢                          (                              cd                ⁢                                  /                                ⁢                                  m                  2                                            )                        xc3x97            area            ⁢                          xe2x80x83                        ⁢                          (                              m                2                            )                        xc3x97            π                                power            ⁢                          xe2x80x83                        ⁢            consumption            ⁢                          xe2x80x83                        ⁢                          (                              W                =                                  voltage                  xc3x97                  current                                            )                                                          (        1        )            
When the discharge initiated from a gap of the display electrodes in the surface type AC PDP propagates in a width direction step by step, the tail portion of the discharge current corresponds to an end portion in the width direction of the display electrode. In this instance, it is possible that the discharge current can be dropped without raising the discharge voltage by providing a dielectric layer having a thickness formed gradually thicker in the width direction of the display electrode.
The blind reduction of the dielectric layer thickness in the related art surface type AC PDP for lowering the discharge initiation voltage to cause a surface discharge in each cell results in an increased capacitance, that causes problems of an increased power consumption and a breakage of insulation.
The related art PDP, with a luminous efficiency below 1lm/W, has a very low conversion ratio of power consumption for causing a discharge to a light.
In the present invention, a thickness of the dielectric layer at a portion the discharge initiates is formed thin while a thickness of the dielectric layer in rest of the portion is formed gradually thicker so that the discharge voltage is dropped and the discharge efficiency is improved without no substantial increase of the power consumption. And, in the present invention, erroneous discharges due to cross talks between the display electrodes are reduced by enlarging the discharge spaces, and a contrast is improved by providing different paths of incident lights.
Accordingly, the present invention is directed to a PDP with a varied thickness dielectric film that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a PDP with a varied thickness dielectric films, for providing a larger discharge space and improving a contrast.
Another object of the present invention is to provide a PDP with a varied thickness dielectric films, which can form a curved surface naturally in coating the dielectric layer.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the plasma display panel includes a plurality of pairs of display electrodes formed on a front substrate, a dielectric layer with a varied thickness formed on entire surfaces of the pairs of the display electrodes, and a protection layer formed to a thickness on the dielectric layer.
In other aspect of the present invention, there is provided a plasma display panel including a plurality of pairs of display electrodes on a front substrate, a first dielectric layer formed on the pairs of the display electrodes to a thickness, a second dielectric layer formed to have a varied thickness in a tapered form on the first dielectric layer centered on a discharge space, the varied thickness being thin at an electric field concentration portion of the pair of display electrodes and thick at an electric field dispersion portion of the pair of display electrodes, and a protection layer formed in a tapered form on the first, and second dielectric layers to a thickness.
The object of present invention can be achieved by providing a PDP including a top panel having a dielectric layer on pairs of display electrodes on a front substrate formed to have varied thickness in a round form, tapered form, or stepped form, and a bottom panel having barriers formed on a rear substrate opposite to the display electrodes, address electrodes and fluorescent material layers formed in succession stacked in the barriers, and frit glass for vacuum bonding the top panel and the bottom panel together.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.